1. Field of the Invention
The present invention relates to the field of cameras. More particularly, the present invention relates to an impact activated triggering mechanism for a conventional disposable camera mounted on a rear-view mirror of a vehicle. In particular, the present invention relates to an impact activated camera triggering apparatus used in combination with a conventional disposable camera wherein the apparatus can be mounted in the vehicle at any point with a field of view.
2. Description of the Prior Art
Generally, when taking a picture, personal attention is required to take a photographic picture of an object. When a vehicle collision occurs, there is almost no way for a driver to manually take a picture at the instant an accident has occurred. An impact actuated switch is required to trigger a camera.
In the prior art inertial switch category, various devices employ spring biased movable masses to open or close an electrical circuit or do mechanical work when the device is subjected to an acceleration. The typical impact sensor utilizes a movable mass that is biased to a normal position by compressed springs or magnetic attraction. The movable mass is often in the form of a spherical metal ball and is constrained to move through a closed chamber against the restraining force of the biasing means upon the chamber receiving a force from the proper direction.
The following seven (7) prior art patents were uncovered in the pertinent field of the present invention:
1. U.S. Pat. No. 2,879,349 issued to Thompson on Mar. 24, 1959 for "Safety Switch" (hereafter "the Thompson patent");
2. U.S. Pat. No. 2,888,530 issued to Horton on May 26, 1959 for "Impact Responsive Camera For Automobiles" (hereafter "the Horton patent");
3. U.S. Pat. No. 3,332,060 issued to Liljequist on Jul. 18, 1967 for "Vehicle Deceleration Signalling Apparatus" (hereafter "the Liljequist patent");
4. U.S. Pat. No. 3,407,667 issued to Doeringsfeld on Oct. 29, 1968 for "Omnidirectional Inertial Trigger Apparatus" (hereafter "the Doeringsfeld patent");
5. U.S. Pat. No. 3,836,738 issued to Baland on Sep. 17, 1974 for "Impact Switch With Inertia Operated Toggle Linkage Actuator Mechanism" (hereafter "the Baland patent");
6. U.S. Pat. No. 5,011,182 issued to Husby et al. on Apr. 30, 1991 for "Velocity Change Sensor With Contact Retainer" (hereafter "the Husby patent"); and
7. U.S. Pat. No. 5,134,255 issued to Tetrault et al. on Jul. 28, 1992 for "Miniature Acceleration Switch" (hereafter "the Tetrault patent").
The Thompson Patent discloses an electrical safety switch. The safety switch serves to interrupt an electrical circuit in a vehicle, airplane or the like, in the event of an accident or impact. The safety switch includes a movable metal ball which is adapted to be moved from a predetermined position upon impact so that the electrical circuit will be interrupted.
The Horton patent discloses a switch of impact type in an electrical circuit. It includes a base of a dielectric material, a permanent magnet which is a horse-shoe design, a steel ball, and a dish with the steel ball located within the dish. The steel ball is kept between the poles of the permanent magnet by the magnetic field between the poles. The magnetic attraction of the steel ball to the poles is intense enough to hold the steel ball in place. Upon impact, the steel ball would be thrown from its position in the center of the dish against the ring encircling the dish, and therefore the steel ball would be in contact with both the dish and the ring. The steel ball contacting both the dish and the ring would close the circuit. The intended, but not claimed, application of this device is the operation of a camera mounted in a vehicle. The switch would energize an electrical circuit causing an electromagnet to depress the push-button of the camera which actuates the shutter in the camera. The switch is mounted remotely from the camera which is mounted in back of the vehicle.
The Liljequist patent discloses an inertia actuated electrical switching device and system responsive to changes in deceleration of a vehicle for varying the amount of light emitted from its rear warning lights. The deceleration sensitive arrangement is used to vary the current flow in an electrical circuit, which is a type utilizing a relatively freely movable mass forming an electrical bridge between two terminals in the circuit. The electrical circuit includes an elongated track, a mass being bias movable relative thereto in response to changes in velocity, and electrical resistance arranged so as to vary the electrical resistance interposed in the circuit dependent upon the relative position between the track and the mass.
The Doeringsfeld patent discloses an omnidirectional acceleration sensor that will provide a unidirectional mechanical output. It includes a frame, a pivot pin, an arm member, a coil spring, and a spherical ball in a cup. When an upward inertial force is received, the spherical ball will tend to remain fixed as the frame moves away from it. The spherical ball will force the arm member to pivot about the pivot pin in a clockwise direction. Similarly, a lateral force causes the ball to move out of the cup so that the arm pivots. The inertial force results in a mechanical movement of both ends of the arm member that can be utilized to perform useful work. The device is specially designed for a munitions fuse.
The Baland patent discloses an inertia switch assembly utilized with an electrical circuit. The inertia responsive switch includes an over center linkage system, switch terminals operatively arranged with the linkage system and effective to move between open and closed positions, and an inertia member operatively connected to the linkage system so as to effectuate an opening or closing of the switch terminals when the inertia responsive member moves relative to the linkage system upon impact or high deceleration of the switch. The switch is sensitive to uniaxial impacts. The switch closes to complete a circuit effective to actuate a transmitter that emits a signal. The switch has special utility in an automatic crash signal device for aircraft.
The Husby patent discloses a velocity change sensor with a contact retainer. It relates to an accelerometer for sensing velocity changes particularly suited for passenger restraint systems in a motor vehicle for deploying an air bag. It includes a housing with contact blades and a contacting element. The contacting element is arranged to move toward the contact blades when a deceleration exceeding a threshold level is sensed. The contact retainer is provided to set the blades in a preselected position so that the blades are simultaneously contacted by the contacting element, thereby improving the response time of the accelerometer. The contact blades are serially connected in an electrical circuit which comprises a battery and an actuating mechanism. The actuating mechanism controls and deploys one or more air bags.
The Tetrault patent discloses a miniature acceleration activated electrical switch. It relates to electrical acceleration activated switches which have a mass movable in a housing against a spring bias in response to an applied acceleration. The miniature acceleration activated switch is responsive to a relatively small axial acceleration in order to close normally open contacts in the switch, in the presence of large laterally directed accelerations on the switch. It includes a hollow cylindrical casing which is closed at one end and the other end is closed by a header having an insulated axial lead wire extending inwardly from the casing, and an electrically conductive ring secured peripherally to the casing. The casing has an internally conical guide sleeve which has a freely rollable massive ball. A piston in the guide sleeve carries a contact member spaced by an expanded coil spring from the lead wire. The piston moves axially against the spring bias such that the contact member contacts the lead wire to close the normally open circuit switch.
Most of the prior art inertial switch patents are designed for use with an electrical circuit. It will be desirable to eliminate the electrical output and rely entirely upon mechanical functions for impact activated triggering mechanism for a camera.
None of the prior art mechanical inertial switches are desirable for impact triggering of a vehicle camera. Most of the mechanical inertial switches require a very large impact for triggering, such as that associated with munitions or an aircraft impacting the ground at high velocities. Another category of inertial switches, mostly electrical, are designed to activate automobile air bags upon severe impacts. These are particularly designed to operate above some high threshold and to avoid false alarms. A vehicle camera trigger should be sensitive to less severe impacts.
The major design problem for a mechanical inertial trigger for a vehicle camera is that the trigger must provide a relatively large actuation force (in excess of one half pound is required to depress the camera shutter release button), but must be capable of activation by relatively low impact loads from any lateral direction on the order of less than one ounce.
In addition, a vehicle camera mechanical impact activated trigger should be designed for convenient location and mounted in the vehicle to facilitate service and manual operation by the vehicle occupants, while not interfering with other vehicle operations and uses.
One of the assignees of the present invention is the patentee of U.S. Pat. No. 5,262,813 issued to Scharton on Nov. 16, 1993 (hereafter "the '813 patent"). The '813 patent discloses an impact activated triggering mechanism for a camera mounted in a vehicle. The '813 patent introduced a sliding motion for triggering of a camera which occurs in a high intensity impact. The impact is sensed by a sliding weight which is configured so that the deceleration or acceleration applied in any direction in a horizontal plane will move the camera relative to the sliding weight and trigger the camera.
The inventor of the present invention has made significant improvements on the '813 patent, in which are as follows: (a) implementations have been identified which provide for more reliable operation when a desired acceleration threshold is exceeded and which reliably maintain the untriggered configuration when the desired acceleration threshold is not exceeded thus preventing incremental inadvertent triggering; (b) means of replacing the sliding motion with rolling motion to make the device more sensitive and repeatable due to less dependence on uncertain environment dependent coefficients of friction for low intensity impact, while sliding occurs for higher intensity impacts, have been defined; (c) means to make re-cocking easier have been defined; (d) means of alignment independent of the mirror back surface shape have been defined; (e) means of integrating the triggering mechanism with the mechanism of a camera have been defined; and (f) details of designs which minimize obstruction of the driver's view, provide chimney effect cooling, protect the camera mechanism from damage following triggering, provide an integral lens shield and enclose functional components for improved appearance have been described.